3 What, then, could I do? Should I not hear? But I could not close my ears with the wax of the old fables. Should I utter what I heard? But I was bound to be on my guard in my words against that which I feared in your commands, namely, lest some deed of blood should be committed. Should I keep silence? But then my conscience would be bound, my utterance taken away, which would be the most wretched condition of all. And where would be that text? If the priest speak not to him that errs, he who errs shall die in his sin, and the priest shall be liable to the penalty because he warned not the erring.
Source: Letters (New Advent)